Telegraph system



March 26, 1940. v. P. THoRP TELEGRAPH SYSTEM Filedl April 22, 1939 35 iore. When a marking signal is being received, the 35 Patented Maize, 1940 y y 25194;918i

'UNITI-:Dl STATES rTEN-tossica--- f TELEGRAPH SYSTEM Vaughn P. Thorp, Hohekus, N. J., assigner te Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York lAppli-lehnen April 22, 1939, serial Ne. 269,505

12 claims. (o1. 17e-5s) This inventionlrelates to improvements in carnected to, said carrier circuit by means of a subrier telegraph circuits and more particularly `to scribers telegraph loop circuit. i

an improved breakingV feature in a carrier tele- Fig. 2 of theassociated drawing discloses the graph circuit interconnected to half duplex loop improved breaking arrangement applied to atelec 5. CilelltS- Y graph connection involving a carrier telegraph' 5 An object of this invention is to provide an im# circuit'and a 'plurality of `local telegraph stations f proved breaking feature in a carrier telegraph connected to said' carrier circuit by means of a circuit. telegraph hub circuit." v

A more speciiic object of this invention is to In the circuit per` Figl a lllllllbel f Celliel l provide improved means for breaking a sender channels are indicated as connected throughiil- 1o transmitting over a carrier telegraph channel to teIS and multiple@ t0 tWO pairs Of conductors-IMv a single telegraph station connected to a suband IZB and 23 and 424,l respectively, extending scribers loop circuit. to a distant station. vConductors l2| `and' [22 Another more specific object of this invention serve in transmitting signals from the subscribers is to provide improved means for breaking a station 425 at the right of Fig. l or for similar 15u sender transmitting .over a carrier telegraph stations connected through their respective filters channel to a pluralityof telegraph stationsall of t0 the distant Carrier SttiOIl- Conductors i which are interconnected by means of avtelegraph end SelVe in leeeiVillg SglleiS transmitting hub circuit. from the distant carrier station tothe subscribers 2n A feature of this invention is a, break relay in station 25 or other similar stations-through their 20 A which an armature and only a single contact are respective Afilters. Other subscribers stations f` required. f may be connected Vthrough individual sending A further feature of this invention is an arfilters Such as it and the same 'transmitting rangement for reducing Contact troubles on a, conductrs l2| and |22 to the distant central 25 break relay by means of passing a low valued cur- Carrier Statioll- FiOi that poillt they may be 25 rent of but one polarity through an armature and extended through PIODeI. itefS t0 Othei" Sllba single contact. scribers facilities associated with the distant cen- A further feature of this invention is an artrai Ocey y I rangement wherein the adjustment of the break Similarly, a' plurality of subscribers circuits relay is unimportant. may be connected through sending filters at the'30 A further feature of this mvennonis that in distant Stationnto the receiving carrier pairy |23 the case 0f the application to ahub C11-cuit the and 424. Receiving filters such as |04 separate transmission path for the received signals inthe. receiving sgnalsand impress them. 0n the" cludes only one relay instead of two as heretopropel OOPYCYCuitf A further feature is that the break relay is Output 0f 2.1 generator: Such as H5 ai theidistam? used for breaking only and does not repeat Sigl Station, will be passed by a filter, transmitted over nals. conductors IES and 124, passed by filter M3,

A further feature is that the break feature amplified by amplifier ,m5,.and impressed as an ai 40 herein does not require the opening of .any of 4ternating voltage between the grid and cathode 4.0 the eceiving relay windings for breaking .pup of rectiier tube lill. -Current will flow from plate poses battery |25 through the top winding of polar relayk A further feature is that the arrangement of Illl, from the vplate to the cathode of tube |01 and the break feature herein facilitates changing from to ground Polar relay' i w is normally biased by balanced loop to hub or"telegraph service board a. Currem-owmg from battery Z5 through the i bottom winding of relay H0 and resistance |09 opel ation greatly leducmg the number of Wmng to ground. The effect of the current through the changes necessary at Conversion top winding of relay HQ, which tends to operate These and other features will become apparent the armature of Sad re'lay to the right pre from the description which follows when read in ponderates over the effectof the Current through 50 relation With the associated diaWilgthe bottom winding, which latter tends to oper- Fig Gf the associated drawing m5010565 the atesaid armature to the left, and the armature implOVed breaking ai'alemeflt applied t0 e is operated to its right-hand or marking contact. telegraph COlllleCtiOll involving a carrier tele- The output of the distant generator is shortgraph circuit and a local telegraph station concircuited for the spacing condition. Receiving 5eA lter |03 then passes no current. Biasing battery |06, impressed between the grid and cathode of tube |01 with its negative terminal connected to said grid, is effective to cut off the iiow of current through the top winding of polar relay H0. The effect of the current through the bottom winding of said relay then operates its armature to engage its left-hand or spacing contact. Thus marking and spacing signals may be received and repeated by relay H0.

While the armature of relay H is in engagement with its marking contact, negative battery is connected over a circuit through said marking contact and armature to the apex of relay I I I where a parallel circuit is formed. One branch of said parallel circuit extends through the bottom or biasing winding of relay III, the bottom winding of relay II 2 and resistance H4 to ground I I9. The effect of the current through the bottom windings of relays III and H2 is to tend to operate the armature of said relays to the left to engage their spacing contact. This effect is overbalanced, however, by the effect of the current owing in the other parallel branch of the circuit through the top windings of relays III and H2 which preponderates to hold the armatures of said relays at their right-hand or marking contacts. The circuit through this parallel branch may be traced through the top windings of relays IH and H2, resistance H3, the top conductor of the subscribers loop to subscriber's station |26. There it passes through the contacts of key H6, the winding of receiver l. II'I and thence through the bottom conductor of the subscribcrs loop to the positive terminal of battery |20 and through said battery to ground I I9. `For this condition the battery of the marking contact of relay H0 is in series with batters7 I 20 and receiving magnet II 7| is energized. For

the spacing condition when the armature of relay ||0 is operated to engage its left-hand or spacing contact, the batteries are opposed and receiving magnet II'I is deenergized. The mechanism associated with the receiving magnet HI which may be the well-known sounder or teletypewriter follows the marking and spacing signals of relay H0. The armatures of relays III and I I2 are maintained in engagement with their -right-hand or marking contacts for both the marking and spacing conditions of relay H0, as when the armature of relay H0 is engaged with its spacing contact the current through the bottom windings of relays III and H2 is reversed in direction and its effect is then to operate the armatures of said relays to the right to maintain them in engagement with their marking contacts.

In transmitting in the opposite direction from station |26 toward the distant terminal, the contacts of key H6 are alternately opened and closed. The armature of relay H0 is held on its marking contact while signals are being sent from station |26 as the output of the distant carrier generator, corresponding to H5, is impressed on the line to maintain relay H0 in the marking condition. While key H6 is closed, the armature of relay H2 is maintained in engagement with its marking contact and the output of carrier generator H5 is impressed through sending filter |02 on the transmitting pair IZI and |22. When the contacts of key H6 are opened, the top winding of relay H2 is deenergized and the effect of current flowing through armature of said relay to engage its spacing contact. This short-circuits the output of carrier generator H5 and no current flows through lter |02 resulting in a spacing signal at the distant terminal. Thus marking and spacing signals are transmitted from local station |26 to the distant station.

If signals are being received at station |26 and the subscriber thereat wishes to break the sender at the' distant station, the break key is opened. This deenergizes the top windings of relays III and H2. When the next marking signal is received by relay H0, if it is not then receiving a marking signal, the armatures of relays HI and H2 are operated to engage their spacing contact. A permanent spacing signal is transmitted to the distant station when the armature of relay H2 remains in engagement with its spacing contact. When the armature of relay I I I is in engagement with its spacing contact, a circuit may be traced from battery |25, through the top winding of relay IIEI, resistance |08 and the armature and spacing contact of relay III to ground. The effect of the current through the top winding of relay H0 for this condition is such that the armature of said relay is maintained at its marking contact regardless of Whether or not signals are being transmitted from the distant station. Thus the transmission from the distant station is stopped or, as it is expressed in the art, the receiving station breaks the sender.

Fig. 2 discloses an arrangement for applying the new break feature to a hub circuit connected to a carrier circuit. Only one subscribers station 226 and its associated loop is shown connected to the hub which is represented by point 233. A number of subscribers station and loop circuits will ordinarily be connected to the hub. A. group of subscribers associated in a particular hub will be interconnected by one carrier channel to the distant carrier station. Other hub circuits or individual subscribers loop circuits may be impressed on other carrier channels on the same four-wire circuit. As in Fig. 1, the iilters for permitting this are indicated in Fig. 2 by lters 20| and 204. The relays shown in Fig. 2 are in their marking positions. For the marking condition the output of a generator such as 2I5 connected at the distant station is being received over conductors 223 and 224 through lters 203 and amplier 205 and is being impressed as an alternating Voltage between the grid and cathode of vacuum detector tube 201. Current flows from plate battery 225 under control of said Voltage through the top winding of relay 2I0 to the anode of tube 201, thence to the cathode of said tube to ground. The effect of this l current is to tend to operate the armature of relay 2IIl to the right to engage its marking contact and it preponderates over the effect of the current owing from battery 225 through the bottom 'winding of relay 2I0 and resistance 209 to ground, which tends to operate the armature of said relay to its left-hand or spacing contact. The armature of relay 2I0 is therefore operated to the right to engage its marking contact. For this condition a circuit may be traced from battery 235, through the top windings of relays 2II and 2I2, resistance 2|3, marking contact and armature of relay 2I0, through the hub point 233, armature and marking contact of relay 230, bottom winding of relay 220 and resistance 22'I to battery 236. The voltages of batteries 235 and 236 are equal and they are opposed in polarity. No current flows through this path, therefore, for this condition. A path may also be 2,194,911?. traced from battery' 235,l through the bottom windings of relays 2H and 2l Zand resistance 2M to ground. The effect of this current holds the armatures ofrelays 2H and 212 `in engagement with their right-hand or marking contacts. A path may also be traced from battery 236, through resistance 23E and the top winding of relay 228 to ground.- The eiect of this current isto operate the armature of relay 228 to engage its right-hand or marking contact. When the armature of relay 228 isl in engagement with its marking contact, a circuit may be traced, from` negative battery, through marking contact and armature of relay 28` to the apex o-f relay 23E) where it divides to form parallel branches. One branch may be traced through the lbottom winding ofyrelay 23B and resistance 232 to ground 2| The other branch may be traced through the topfwinding of relay 23?), resistance 22S, top conductor oi' the subscribers loop to the subscribers station 226i. There it passes through the contacts of key 285 and receiving magnet 2H'. Then it extends through the bottom conductor of the subscribers loop'to the positive terminal of battery 22B and through said battery to ground 2|S. For this condition the batteries at each end of the loop are in series and the effect of thecurrent through the top winding of relay 23B, which tends to operate the armature of said relay to engage its right-hand or marking contact, preponderates over the effect of the current through the bottom winding of said relay, which tends to operate the armature of said relay to engage its left-hand or spacing contact and the armature is held in engagement'with its right-hand or marking contact. For the transmission of a spacing signal from the distant st'ation to station 226 the output of the generaton,

. ate the armature of said relay to the left to engage its spacing contact. This connects ground from said spacing contact, through said armature. to the hub point 233 and thence through the armature and right-hand or marking contact of relay 232, the bottom winding of relay 228 and resistance 227 to negative battery 235. The effect of current flowing through the bottom Winding of relay 222 for this condition preponderates over the effect of current through the top winding of said relay and the. armature of said relay is operated to engage its left-hand or spacing contact. -This connects positive battery to each end of the subscribers loop, deenergizing vthe top winding oirrelay 232. The current through the bottom winding of relay 232 is reversed and it is, therefore,` effective to maintain the armature of said relay in engagement with its right-hand or marking contact. Receiving magnet 2li is alternately energized and deenergized to operate a sounder such as 218 or a teletypewriter. Since other4 subscribers loops may be connected to the hub point 233 by means of conductor 23d, signals received by relay 2li) will be impressed through the armature of marking contacts of relays similar to 23B on the bottom windings of relays corresponding to relay 228 in each case and relays correspondingto relay 228 will impress the received signals on their) respective y subscribers loop circuits.

If the subscriber at station 226,' or any other subscriber connected to the hub, wishes to break,

the contacts of the break key or a correspond-f ing key at any of the other stations connected to the hubwill be opened. Relay 230 ora co1'- responding relay in any of the other loops which has been opened will have its top winding deenergized andits armature will be actuated to' engage'its' spacing contact under the iniiuence4 of current' in its bottom or biasing winding.y A circuit may then be traced from ground, through Ithe spacing contact and armature of relay 23B or of any similar relay, to hub point 233, through the armature and marking Contact of relay 252, resistance 2I3, top windings' of relays l2I2 and 2H to negative battery 235. The effect of current through the top windings of relays 2li and 222 will preponderate over the 'reflect of current through the bottom windings of said relays and the armatures of said relays will be operated to the left in each instance to engage their spacing contacts. engagement with its spacing contact, a circuit may be traced from battery 225, through the `top winding of relay 2li! 'and resistance 2%, through the armature and left-hand or spacing Contact of relay V2H to ground. The effect oi' current lowingthrough the top winding of relay 2l!) for this condition maintainsthe armature of relay 250 in engagement with its right-hand or marking contact regardless of whether or not signals are being received from they distant station. Whenthearmature of relay 2i2 remains in engagement with its left-hand or` spacing contact, the output of generator 215` is short-circuited and the distant station receives a permanent spacing signal which interrupts his sending.v

The breaking arrangement shown in both Fig. l and Fig. 2 results in the following advantages common to both individual loop and hub circuit o-peration.

Since no current flows through the topwindings of relays I It] and 232 while a spacing signal is being received, thefcurrent: required `through the bottom windings of these relays need be only great enough to operate their armatures to their spacing contacts for this condition. A very small current is'adequate for this purpose since the polar receiving relays til and 2 lo are quite sensitive. The currentl through the tcp windings, therefore, necessary to overcome the effect of the current through the bottom windings when a break signal is being transmitted toward the dietant station, may be correspondingly small; rAy

current of approximately 4 milliamperes has been found adequate for this purpose. Thus, the current through the spacing contacts of relays li l and 2| I need be but 4 milliamperes for the breaking condition. Further, but one pair of contacts is required on each relay, namely, a spacing contact, and its cooperating `contact on the armature. The set of marking contacts is not required. Current of one polarity only is passed through the armature and spacing contact of each of relays l H and 2l i. This. results in long Contact life for these relays with very little maintenance being required.

Further, the adjustment of thebreak relays is unimportant. The break relays ill and 2H follow signals transmitted toward the distant station 4but they do not repeat signals. Since their only essential function is to close their spacing contacts in response to` a break signal trans-` When the armature of relay 2H is in mitted toward the distant station, whether or not they are biased is unimportant.

What is claimed is:

1. In combination with a carrier telegraph circuit, an arrangement for breaking the sending of telegraph signals over said circuit comprising a. receiving relay, a line Winding thereon, a break relay, an armature and a single contact on said break relay and means responsive to the engagement of said armature and said contact for increasing the current through said line winding.

2. In a telegraph system, a carrier telegraph receiving channel, a receiving relay, a winding on said relay in series in said channel, a break rela a winding on said break relay in series with a subscribers loop circuit connected to said carrier current, an armature on said break relay, a connection between said break relay armature and said receiving relay winding, means cooperating with said break relay armature for increasing the flow of current through said receiving relay winding in response to a break signal.

3. In a telegraph system, a first telegraph central station, a second telegraph central station, a carrier telegraph transmitting channel and a carrier telegraph receiving channel connecting said stations, a local telegraph station, a differential telegraph loop circuit connecting said rst central and said local stations, a receiving relay, a winding on said relay in series in said receiving channel, a break relay and a. sending relay, a winding on said break and a winding on said sending relays in series in said loop, an armature on said break and an armature on said sending relays, means responsive to the opening of said loop to operate said armature at said break relay to increase the current through said receiving relay Winding to prevent further operation of said receiving relay armature and means on said sending relay responsive to said opening to operate said armature on said sending relay to transmit a steady spacing signal over said transmitting channel.

4.` In a telegraph system, a iirst and second telegraph station,A means comprising a carrier telegraph transmitting channel, a carrier telegraph receiving channel and a differential telegraph loop circuit connecting said stations, means comprising a break relay in said loop circuit having an armature and a single actively cooperating contact for interrupting the transmission of telegraph signals between said receiving channel and Said loop circuit and means for transmitting simultaneously a steady spacing signal over said carrier transmitting channel, both of said means `responsive simultaneously to identical control means at said second station. l

5. In a telegraph system, a carrier telegraph circuit, a sending subscribers telegraph station and a receiving subscribers telegraph station connected thereto, breaking means connected to said receiving station responsive to control means at said receiving station for interrupting the transmission of signals from said transmitting station, said breaking means comprising a polar relay having a winding in the transmission path between said stations and an armature operatively engaging one contact only.

6. In a carrier telegraph system, a carrier telegraph transmission path, a receiving relay having a winding in said path, means in said system for receiving a current of a first value through said winding for a marking signal and a current of a second value for a spacing signal and means for changing the current value through said Winding to a third value fora break condition.

7. In a carrier telegraph system, a carrier transmission path, a receiving relay, a rst winding thereon in series in said path, a second winding thereon, an armature and a marking and spacing contact thereon, means for conducting an electric current through saidsecond winding to bias said armature to tend to engage said spacing contact, means for passing an electric current of a first and second value through said first winding to operate said armature to engage itS marking and spacing contacts alternately in response to received marking and spacing signals, and breaking means for increasing the current through said first winding to hold said armature in engagement with its marking Contact While a spacing signal is being received through said iirst winding.

8. A first and a second telegraph station, a iirst and a second carrier telegraph terminal, a first telegraph loop circuit connecting said rst station and said iirst terminal, a second telegraph loop circuit connecting said second terminal and said second station, a carrier telegraph circuit connecting said iirst loop to said second loop through said terminals in tandem, a receiving relay having a winding in series with said carrier circuit at said second terminal, means connected to said relay for impressing marking and spacing signals on said second loop, and relay means in said second loop for augmenting the marking ampere turns in said receiving relay while a spacing signal is being received by said receiving relay to maintain said receiving relay in its marking condition when said second station transmits a break signal.

9. In a telegraph connection comprising a fourywire carrier circuit and a subscribers loop and station circuit, a break relay having a winding in series with the loop, an armature and a contactcooperating with said armature both on said relay, a telegraph receiving relay connected to said carrier circuit and means for establishing an operative electrical circuit comprising a winding on said receiving relay, said armature and said contact when a break signal is transmitted from said station circuit.

l0. In a telegraph system, a carrier telegraph receiving channel, a subscribers telegraph loop and station circuit connected thereto, a receiving relay, an armature, a marking and spacing contact cooperating therewith and a first and second winding all on said relay, said iirst winding connected in series in said channel, a break relay connected in Said loop, an armature and a contact cooperating with said armature all on said break relay, means for transmitting electric current through said first Winding for a marking signal, means for reducing said current substantially to zero for a spacing condition, means for supplying a biasing current of the order of 2 milliamperes through said second winding to operate said armature on said receiving relay to engage its spacing contact, and break signal control means in said loop for operating said armature on said break relay to engage its cooperating contact to supply current of the order of 4 milliamperes through said ilrst Winding to overcome the effect of said biasing current when a break signal is transmitted from said station.

1l. In a telegraph connection between a carrier telegraph circuit and a direct current telegraph circuit, the method of reducing maintenance required by break contacts cooperating with a receiving relay to break a distant sender which includes (l) receiving carrier current for the marking condition, (2) receiving substantially Zero current for the spacing condition, y(3) using current of a .value only slightly greater than zero Value for biasing While said zeror current is being received, and (4) overcoming said bias by a current of a value only slightly Agreater than said biasing current to maintain the marking condition, thus requiringr only a small current through said breaking contact for the receiving relay when a break signal is transmitted toV the distant carrier station.v

" station for receiving telegraph signals from said stationand .means connected to said relay responsive to breaking means in any of said v1001:) circuits for preventing the operation of said relay when a break signal is transmitted from any of i0 said loopcircuits.

' f VAUGHN P. THORP. 

